1. Field of the Invention
The present invention relates generally to a control device having both analog and digital portions and, more particularly, to a grounding arrangement for such control device.
2. Description of the Related Art
A control device is disclosed in German Utility Model 87 15 073.5.
This control device has analog modules and digital modules that are arranged on a carrier plate. The upper side of the carrier plate has printed connecting lines for the modules, terminal contacts for connection to signal lines, and terminal points to ground. A planar grounding layer to which the grounding terminal points on the upper side are connected over the shortest path is arranged on the lower side of the carrier plate. Connectors that pass through holes in the carrier plate serve this purpose, so that extremely low impedance connections to ground are provided.
Despite the advantageous structure of this known device, a high frequency emission which proves disturbing in some cases has been measured at such control devices. This is particularly true in the case when lines leading from the control device, and in particular the grounding line, forms a cable tree together with other lines that lead to other electronic devices. A very tight coupling between a number of devices which can lead to mutual disturbances thereby arises.